Pneumatic hydraulic pumping apparatus



Aug. 2, 1960 s. v. SMITH 2,947,144

PNEUMATIC HYDRAULIC PUMPING APPARATUS i Filed Aug. 19, 1957 3Sheets-Sheet l n" JAMUEL I/'M/TH INVENTOR.

n 1MM/wf Aug. 2, 1960 s. v. SMITH 2,947,144

PNEUMATIC HYDRAULIC PUMPING APPARATUS i Filed Aug. 19, 1957 3Sheets-Sheet 2 'g. a 7: /g. 5. 5

Je" I JAM/Ez. HJM/TH [Z4/SE1 INVENTOR.

l ff BY M t:

f7 fram/Ey Aug. 2, 1960 s. v. SMITH 2,947,144

PNEUMATIC HYDRAULIC PUMPING APPARATUS Filed Aug. 19, 1957 5 Sheets-Sheet3 F/g.4. fr

AMI/EL 1./ J'M/ TH INVENTOR.

rrORA/EY access to .the well ,for :servicing purposes.

2,947,144v Y PNEUMATIC HYDRAULIC PUMPING APPARATUS Samuel V. Smith, LongBeach, Calif., assgnor to Pneu- Ely Co., LongBeach, Calif., acorporation of Caliomra t Filed Aug. 19, 1957, seri. No. :678,807 1oClaims. (icl. ntl-"52) This invention relates generally to apparatusused for pumping wells, and more particularly has to do withimprovements in .Huid pressure powered pump jacks operable to raise andlower well pump rods and the like.

In general fluid pressurized pump jacking units presently in use arecharacterized as regards their construction in relation to the well headas extending to a considerable height above the ground and over thewell, it being conventional practice to mount a large pumping assemblyvertically ,over the pump rod for supporting the latter and forreciprocating it up and down. However, at the present time there isincreasing public and civic expression of .a need for restricting theobservable size of such equipment, particularly in residential areaswhere the benefits ofl petroleum production are recognized and soughtafter at the expense of accommodating to the necessary presence oftheproduction machinery.

Accordingly, it is a Vmajor object of the present invention tosubstantially limprove the construction and especially the arrangementofwell pump jacking units so as to .minimize the apparent size thereof tothe observer, while ,at the same time increasing the reliability andimprovinglthe operation -of the equipment. To this `end, the inventioncontemplates the provision of apparatus for vertically reciprocating awell pump rod or .the like projecting above ground surface level,comprising a plurality of vertical .cylinders spaced apart laterally sothat they may besunk downwardly into the ground in laterally offsetrelationto the well, together with pistons ,reciprocable up and down inthe cylinders and means for supporting the pump rod atY its ,projection.above yground by the pistons and for reciprocating the `supported rodup and down in response ,to piston reciprocation. Ihe pistons are thenreciprocable below groundsurfacelevel rby application of fluidpressureto them in ,the manner .to be explained, so that alarge part of theequipment needed to lift `and lower ,the pump vrod is ,underground .andout of sight of the observer. Also, there lis a VYof jacking equipmentover the well head itself, facilitating ready The ground surface levelreferred to will be understood to meanthe surface immediately around thewell head, so that the surface may comprise the `bottom of a-,shallowopen pit into Iwhich all of the `equipment is received.

In the carrying out `of the invention to Suit vthe purpose described,the pistons and cylinders 'are preferably ,laterally .spaced on oppositesides of a center corresponding to the well location, so that anaboveground .cross head structure interconnectingthe pistonrods may,bridge over the well pump rod for reciprocating ithe latter as thepistons are ,displacednp Land down in thelcylinders. Such displacementis yeffected by means interruptedly cornmunicating `hydraulic pressure,`for example, -toatirstpair of jacking tpistons n. opposi te fsides rofthe *well `and tending interruptedlgyttoraise `the,p tnnprod, :andalso.by. means constantlyrcommuuicating gas pressurevtoasecondpair ofbalance ,pistons likewsespaced onopposite `sidesof the Well andunderground, tending constantly to raise the arent pump rod. When, ascontemplated, the pressure communicated to the balance pistons isinsufcient alone to raise the pump rod, thelattcr is lifted only duringcommunication of hydraulic pressure to the-'jacking pistons,interruption of such communication allowing the pistons to drop on thepump rod downstroke, the rate of drop being controlled by restricting`the backflow of hydraulic uid pushed from the Vcylinders by the pistons,as will be explained.

Another major object of the invention concerns the provision of valvemeans responsive to reciprocation of the pistons for controllinginterruption of hydraulic uid pressure communication to the pistons, thevalve placing pump discharged vhydraulic fluid in communication with thejacking pistons on the pump rod upstroke, and placing fluid backfiowtherefrom in communication with the pump intake during the pump roddownstroke, the net effect of the latter being to brake and therebycontrol the dropping rate ofthe pump rod. At this time, the pumpdischarge is placed in communication with the balance pistons so thatthe pump then discharges against the gas pressure constantlyVcommunicated rto the balance pistons. i

Other .additional objects of the invention include the provision ofmeans for maintaining a predetermined pressure differential between thepressure exerted on the hydraulic fluid by the jacking pistons under theweight of the pump |rod load, andthe gas pressure communicated from agas reservoir to the balance pistons via hydraulic liquid, so that asthe load increases` or decreases, the balance pressure may likewiseincrease or decrease to balance the load and thereby permit thehydraulic fluid pump to operate lfor effectively lifting the-pump rod inthe well.

These and other vfeatures and objects of the invention, as Well as thedetails of an illustrative embodiment, will be more fully understoodfrom the following detailed description of the drawings, in which:`

'Fig 1 is a general view showing in .elevation the pumping apparatus andits relation to the well head;

Fig. 2 is a plan view of the Fig. r1 apparatus;

Fig. 3 is an enlarged vertical Vsection taken through actuatingmechanism for the pilot valve; v j

Fig. 4 is an enlarged View taken in section through a part of the Fig. 3mechanism, the pilot valve and master valve, showing how these operatewith relation to one another;

Fig. 5 is a partial kplan view of Fig. 1 v,showing mechanism used toregulate the gas pressure in a reservoir;

IFig. 6 is a section taken through actuating mechanism usedfor comparingreservoir gas pressureexerted lo n the balance pistons and hydrauliciluid pressure exerted .on the jacking pistons; and

Fig. 7 is a section taken through the lower portion of the gas reservoirillustrating the manner in Vwhichsystem -luid is cooled.

Referring to the apparatus as shown in jF-igs.' 1 `and 2 and generallyindicated at 10, the `latter includes a pair of balance cylinders 11extending vertically and laterally spaced on opposite sides of anunderground well casing 142, indicated in broken lines, andanother pairof jacking cylinders 13 also spaced on opposite sides of the casing, andextending vertically underground. The various cylinders may be supportedon concrete as indicated at 1 4, or merely by the formation itself wherethe structure thereof is sufficient to support'the loads involved. Also,the cylinders Aare :interconnected by a steel ring `shown at 15 belowthe ground surface level 16, thering Apreferably being connected to thecasing l12 so that .jacking Iand Abalance loads may be transferred fromthe pistons and ,cylinders tothe casina The lower ends of all thecylinders 11 and 13 are closed as by means of steel plugs 17, Whiletheir upper ends are internally threaded for receiving cylinder heads 18projecting above the ground level 16. The top surfaces of the headsserve to stop downward travel of enlarged piston rods 19, the lower andrelatively smaller end portions 20 of which are secured within tubularbalance pistons 21 and jacking pistons 22, these latter being guided forup .and down reciprocation by the cylinder heads 18. Suitable packingmaterial 23 seals olf between the pistons 21 and 22 and the cylinderheads so as to maintain hydraulic pressure within the spaces between thepistons and the cylinders during-their reciprocation. j

The extensions 19 of the jacking and balance pistons projecting aboveground surface level 16 are interconnected byV a cross head structure25shown in Figs. 1 and 2 and including transversely extending arms Z6interconnecting the opposite extensions 19 and extending over the wellhead 27 and supporting a central pump rod 28, which is received downwardwithin the casing 12. A suitable interconnection between the cross head25 and rod 28 may be a conventional keeper indicated at 29 into which alocking bolt 30 is threaded for securing the keeper to the rod 28.

Speaking generally with respect to :dow of fluid and liquid to and fromthe jacking and balance cylinders, Figs. l and 2 show that hydraulicliuid is conducted to and from jacking cylinders 13 via lines 33branching from common line 34, while liquid under pressure is conductedto and from the balance cylinders via conduits 35 branching from acommon conduit 36, both the lines and the conduits described openinginto the cylinders underground. While reference in different portionsofthis description will be made to hydraulic iluid and also to hydraulicliquid, it will be understood that these terms refer to a commonhydraulic liquid or fluid, the distinction in terminology being merelyfor purposes of claritica-tion as regards association of liquid withpressure communication to the balance pistons, and ,uid as concernspressure communication to the jacking pistons.

'Further in this respect, the common source of the hydraulic liquid oruid is in the bottom portion 37 of a reservoir tank 38, and its upperlevel upon which gas pressure in the reservoir is exerted iiuctuatesbetween the broken lines indicated at 39 and 40 in Fig. l, associatedwith the extreme downstroke and upstroke positions of the pistonsrespectively. Gas pressure in the reservoir is constantly communicatedto the balance pistons via the liquid in the bottom portion 37 of thereservoir, and the liquid in the conduits 41, 36 and 35, conduit 41shown in broken lines in Fig. l opening into the bottom portion of thereservoir. 4It will be understood that this balance pressure exerted onthe pistons 11 and tending to raise them togetherV withV the pumping`rod is insufficient to accomplish such lifting to a degree which may beovercome by the application of hydraulic fluid pressure to the jackingpistons 13, as will be described, the total pressure then being suicientto lift the pump rod and the string attached thereto in the well.However, upon interruption of hydraulic iiuid pressure communication tothe jacking pistons, the pump rod 28 and the supporting pistons willdrop, such lowering being interrupted before the piston extensions 19strike the cylinder heads 18.

The above described rather small pressure differential needed to effectraising of the well pump rod and supporting pistons is supplied by thepump 42 shown in Figs. l and 2 having its pressure fluid discharge 43connected through a master valve 44 with lines 33 leading to the jackingpistons during the upstroke, and having its inlet 45 in liuid pressurereceiving communication with jacking cylinders via lines 33, 34 and themaster valve 44 during the downstroke movement of the pistons and pumprod. Briefly, in regard to the latter condition and V42 is preferablyused to meter fluid backow from the jacking cylinders to thel reservoirduring the piston downstroke, the constant speed pump regulating thedownstroke speed so that the latter is constant regardless of pressureor vacuum conditions of uid under the jack pistons and hence at the pumpinlet.

Coming now to a description of the master valve 44 referred to inconnection with Figs. l and 2, it is shown in detail in Fig. 4 tocomprise an elongated housing 48 having a bore 49. The latter receives apair of like plugs Si), preferably cast iron, received endwiseoppositely in the bore, the plugs having llanges 51 connected withhousing anges 52 by means of bolts 53. The plugs in turn contain axiallyaligned bores 54 receiving an elongated valve spool assembly 5S whichincludes an axial shaft 56 mounting spools or pistons 57 at oppositeends of the shafts, and intermediate spools or pistons 58, the entirespool assembly being shown in its extreme leftward position in Fig. 4.Leftward and rightward travel of the assembly is effected by thealternate introduction of fluid under pressure from ducts 59 and 60.

In the position of the valve spool shown in Fig. 4 hydraulic fluid fromthe pump 42 flows via pump discharge 43 into the master valve andbetween the spaced ends of the plugs 50. From there the uid ows outwardthrough line 34 connected into the master valve housing, the spools 58confining the flow within the housing to have this described directionduring applicaton or communication of lluid pressure to the jackingpistons for lifting the pump rod. At this time, hydraulic liquid fromthe reservoir enters the master valve through line 46 connected into thehousing 48 and discharges at 61, as indicated by the broken lines inFig. 4, for circulation to the pump intake 45. Therefore, the pressureexerted on the pump intake during the upstroke of the pistons is the.pressure existent in the balance cylinders, and may be convenientlyreferred to as the balance pressure. .As a result, the pump adds to thebalance pressure its characteristic pressure dilerential forcommunication to the jacking pistons for lifting purposes. During thistime, the exhaust outlet 62 from 'the master valve is plugged olf fromcommunication with either line 34 or 46.

On the other hand, when the valve spool assembly is at its extremerightward position as indicated by the broken lines in Fig. 4, hydraulicHuid from the jacking cylinders backows through line 34 into the mastervalve unit and discharges at 62 to the pump intake at 45, while the pumpdischarge 43 is then placed'in communication with line 46 and iluid fromthe pump then flows to the reservoir 38. Under these conditions, thedischarge 61 is plugged olf from communication with lines 34 and 46.

Further in connection with the construction of the plugs 50, theiroutside diameters are annularly reduced opposite lines 34 and 46, in thedischarges 61 and 62, and the thus formed thin walls of the cylindricalplugs are perforated as shown in Fig. 4, to pass hydraulic fluid backand forth.

Another pair of lines 63 and 64 are connected into the master valvehousing 48 opposite lines 34 and 46 to receive hydraulic pressure fromthe jacking cylinders and yfrom the reservoir respectively. These linesare shown in Fig. 5 as extending to a pressure comparing mechanismgenerally indicated at 65, which is enlarged in Fig. 6 and shown indetail. The mechanism includes tubular housing 66 receiving end plugs 67between which a piston 68 is slidable in the housing bore 69. Anoppositely endwise extending pair of rods 70 and 71 conatteignit nectedwith the pistonliiyare guided Withr'endwise revciprocationby plugs67rightwardtravel of the rods beinggopposed by exertion of hydraulic,iluid4 pressure entering the mechanism from line 63, and leftvvardtravel being opposed by hydraulicV pressure from the reservoir conductedviaV line 64 to the `-leftward tace, of the piston `68. Since thebalance pressure communicated to the balance pistons is in general lessthan the hydraulic duid indicated at 72.V However, when the Apressurejdiierential j rises beyond a predetermined arnonnt, as for examplewhere the load rexerted by the pump rod-.carried equipment increasesabove .a certain amount, piston 68 travels to the left and the steppedrod 70 actuates the regulating val-veY lever v'73 to the brokenflneposition shown in Fig. 5. Under these conditions, compressed gassupplied from,V the tank via line 74 to the regulating valve 72, andt-hen normally via line 75 to a clutch indicated at 76, is bled od at7.7 allowing .the clutch to engage. Consequently, the motor 78 which isalways running then drives the compressor 79 through ia V-belt 80engaged by the clutch, and additional gas is compressed into the tank.Clutch *76 may normally `have a spring acting `to urge a movable'sheavetoward the V-belt 80 for engaging same, and a-rnovable piston urging the-sheave away from the V-belt under the iniluence 'of compressed gasfrontline 75.

O11 the other hand, should the hydraulic fluid pressure `from thejaclsing cylinders and communicated .to the mechanism `65 via line 63drop below a predetermined level, vthe pressure trom the tank exertedagainst lthe left `face of piston 68 plus the action of the spring inthe regulating valve 72 will displace the piston 68 and rod 731 to theright, and the latter will actuate .a hleeder valve 81, for bleedingexcess gas pressure in thetank or reservoir from the valve 81 via line82. Therefore, the desired pressure differential will tend to bemaintained as respects therelatiouship between the balance pressure andthe hydraulic duid pressure associated with the balance and jackingpistons respectively.

Turning back to Fig. 4, leftward and rightward travel ofV #the valvespool S is under the control ofa'pilot valve indicated generally at 83,and including elongated housing 84 containing la bore 85 in whichanother valve spool assembly 86 is axially `endwise reciprocable. *Thelatter includes a pair of pistons 87 at opposite ends of lthe .spoolshait 88 and a pair of intermedi-ate and spaced pistons 89 which areaxially endwise movable between Vlbores 90 in which they are shown 'asreceived, and 'bores 91. In the position shown, hydraulic iluid pressurefrom 'the pump discharge at 43 enters 'the housing 84 via `line 92 andows between the spools 89 and outward via line 59 to the master valvefor urging its spool assembly 55 leftwardly to the position in `which it`is shown. vDuring such leftward travel, hydraulic Huid from line 60flows back to the pilot valve and then ont discharge 93 as shown by thebroken lines, through a hand operated valve y94- and to discharge line95 com- Vrnunicating with the pump discharge. Valve 94 may be opened orclosed to the degree as ydesired for restricting backward flow ot duidthroughthe pilot valve and there- A'by controlling the rate at which thevalve spool 55 travels in the master valve assembly, in turn controllingthe stroke of the pump rod 28.

In like manner, when the pilot valve spools 89 are inthei alternateposition received within bores 91, uid from the pump Vdischarge at 4?`iiows into the pilot valve through line 92 and out through 'line 60 tothe master `valve for urging valve spool 55 rightwardly. At

valve 97 and to the discharge 95. As above, valve 97 may be 'adjusted inrelation to valve 94 to control the upward travel .of the pump rod. Y

Shifting of the pilot valve spool 86 in response to' reciprocation ofthe balance piston 21 shown in Fig. 3 is accomplished by operation ofthe actuating mechanism generally shown at 98 to include a verticallyextendingfrod 99 reciprocable up and down by the pis-ton ,extension 19towhich the rod is connected by link 100. The upper end of the rodextends through asleeve 101 carried by the transverse link 100, anda setscrew 102 threaded in the sleeve and engaging the rod, is adjustable topermit control of the rod position relative to the piston extension 19lfor changing the stroke length of the pistons and the pump rod 28.

Actuating rod 99 is movable in a vertically extending fprotectiveunderground tube `103 extending downward lfrom connecting ring15 supporting cylinder 104 through which the rod 99 projects `upward andabove ground surface level 16. .As better shown in Fig.l 4, housing 104contains a cylinder 116 and a piston 105 reciprocable up and down inthercylinder bore 106, with cylinder end plugs 107 guiding the upper andlower piston extensions 108 and 109 projecting through the plugs.Boththe .piston and its extensions are tubular so that the rod 99 mayreciprocate axially therethrough, suitable O-ring seals 110 and 111being provided to seal vof between the piston 105 and bore 106, andbetween the piston extensions and the end plugs 107, all for thepurposes of retaining hydraulic fluid within the bore spaces 112 and 113above and below the piston itself. The fluid in spaces 112 and 1113communicates respectively with the pilot valve lend spools 87 via lines114 and 115, so that the pilot valve spool assembly is displaced endwisein accordance with a change in the direction of travel of piston 105.

Housing 104 contains hydraulic iluid standing at a level above checkvalve intakes 117 to extensions 118 and 119 of lines V114 and 115respectively within the housing 104, it being understood that liquid maybe drawn into those extensions and into the bore spaces 112 and 113 whensuction pressures exist therein. Aiso, suitable ball check pressureYrelief valves 120 `are connected into the ttings 121 and 122 joined tothe cylinder 116 and through which fluid in "lines v1114 and-communicates with the bore spaces 112 and 113 respectively. Thus,

should fthe'lpressure developed by displacement of piston -105`lexceedfa predetermined level, hydraulic huid will `escape into the`duid-chamber 123 'in housing 104.

`Refer-ring Vto the operation `of the actuating mechanism indicated vat98 in Fig '13, it will be seen that upward displacement of the actuatingrod 99 bythe balance piston extension 19 will bring a shoulder 124 atthe lower end of rod 991`into engagement with lower end of pistonextension 109, vand further upward travel of Vrod 99 will displaceVpiston 105 vupwardly `in bore 106, eiecting a shifting of the Apilot`valve spool assembly v.'56 from the position shown in Fig. 4 to itsalternate position. Conversely, downward travel of 'the'balance pistonextension irl-9 will -cause link 100 to engage the upper end of thepiston extension 108;, thereby displacing piston 105 .downwardlyin'bore106 and eitecting shifting of the pilot valve spool :assemblyo to theposition shown in Fig. 4. Operation Arcomplete .cycle of operation yofthe pump jacking apparatus'will now be described. At the completion ofthe pump rod downstroke and at the beginning of its upstroke,1the lpilotValve and master valve spools S6 and u55 are inthe position -showninlFig. 4, `facilitating `direct communication of hydraulic fluid pressurefrom the ,pump discharge 43 -to the jacking pistons ,'22, via lines33..and .3.4, vthe spaces lbetween the jacking cylinders '13 andthepistons 21, Vand @the i clearances between the cylin- .ders of .the.fjaclringcpistonheads 32. At this time, fluid :stands lat level 39inthe reservoir tank 38 asshown in ',Fig. l, and during the jacking pistonand pump rod upfstroke, fluid Viiows from the reservoir to the pumpintake 45 via the master valve, as explained above. The Vpump is drivenby theV motor 78, as by the V-belt drive shown in Figs. l and 5,preferably at constant speed, so that the pump rod 28 is steadilylifted, and the liquid level in the reservoir tank 38 falls to thebroken line level indicated at 40. n 4

Near the completion'of the pump rod upstroke, the actuating rod 99effects the lifting of the piston 105, with consequent shifting of thepilot valve and master valve spool assemblies 86 and 55. This time,hydraulic fluid in the jacking cylinders is placed in communication withthe pump intake 45 via the master valve, as explained above, and thepumpv discharge 43 is connected with the iluid in the reservoir 38, alsovia the master valve and lines 46 and 36 as shown in Fig. 2. Therefore,the only hydraulic liquid pressure tending to lift the pump rod 28 isthe balance pressure exerted on the balance piston head 31, so that thepump and rod begins its downstroke, together with the jacking andbalance pistons. During such downstroke, the pump 42 driven at constantspeed brakes the downward travel of the jacking pistons since hydrauliciuid under pressure exerted by those pistons can iiow through the pumponly as regulated by the pump speed. Therefore, the pump meters orrestricts hydraulic iiuid ow toward the reservoir 38, and the level offluid in the reservoir rises at aV constant rate in accordance with suchmetering to the upper level 39 at the completion of the downstroke.

Oil standing in the lower section of the reservoir is convenientlycooled by air blown between the outer and inner shells 130 and 131 bymeans of a fan 132 rotated by pump shaft extension 133 in the inlet 134,as indicated in Fig. 7. After passing in cooling relation to the oilstanding within the inner shell 131 of the reservoir, air flows throughthe outlet 135.

Reference to Fig. l shows the pump 42, reservoir tank, compressor, andvalves 43 and 44 mounted on a frame 137 standing on the ground, whereasthe actual jacking cylinders and pistons extend well below ground level,It is of course understood that the reservoir tank 38 may be mountedhorizontally to decrease the height of the equipment standing aboveground.

I claim:

l. An apparatus for vertically reciprocating a loaded rod at a constantuniform rate onthe downstroke thereof irrespective of variation of themagnitude of said load on said rod which includes: a plurality ofsubstantially vertically extending and laterally spaced cylindersadjacently disposed to said rod; piston means reciprocal up and down insaid cylinders; a reservoir partially filled with hydraulic fluid andhaving a quantity of gas at at least a predetermined minimum secondpressure situated thereabove; a source of gas at a pressuresubstantially higher than said second pressure; a positive displacementpump; a prime mover which when operating continuously drives said pump;first valve means which include a movable valve member capable ofoccupying first and second positions; first conduit means which whensaid valve member is in said first position have said iiuid fiowingtherethrough from said reservoir to the suction of said pump to bedischarged to a first portion of said cylinders at a first pressurehigher than said second pressure to cause said pistons therein to riseand raise said loaded rod; second conduit means which when said valvemember is in said second position and said loaded rod moves downwardlyfrom the top of its stroke have said hydraulic iiuid owing therethroughfrom said first cylinders to the suction of said pump, and the dischargeof said pump being conducted by said second means to said reservoir,with the rate at which said uid is pumped through said pump solelydetermining the rate at which said loaded rod moves downwardly on thedownstroke thereof; means responsive to the movement of said loaded rodthat move said valve member to said first position at substantially thetermination of the downstroke lofsaid rod and to said second position atsubstantially the completion of the upstroke by said rod; Ythird conduitmeans extending between said reservoir andv said second portions of saidcylinders to force said pistons therein by fluid at said second pressureto support a predetermined fraction of said load on said rod on both theupstroke and downstroke thereof; and means sensitive to the pressure ofsaid gas in said reservoir and said uid at said first pressure thatbleeds gas from said reservoir, or admits gas from said source to saidres- -ervoir to automatically maintain a predetermined differentialinpressure that is substantially constant between said rst and secondpressures to 4force said pistons in said secondV portions of cylindersto support said predetermined fraction of said load on said rod on boththe upstroke and downstroke thereof, even if the magnitude of said loadover a period of time varies.

A2. An apparatus as defined in claim l in which said source of gas underpressure is a gas compressor, and

-an air pressure controlled clutch is provided capable of driving saidcompressor together with transmission means connecting said clutch tosaid prime mover, and the air pressure on said clutch varied to placesaid clutch `in a compressor driving position to supply gas to saidreservoir until the pressure of said gas in said reservoir has risensufiiciently to establish said predetermined differential between saidfirst and second pressures by opand said first passage, a second conduitconnected to the l interior of said reservoir and said second passage, athird conduit connected to the suction of said pump and said thirdpassage, a fourth conduit connected to said fourth passage and theinterior of said `first portions of said cyl- Yinders, with said memberdisposed in said body, and

when said member is occupying said first position establishingcommunication between said first and fourth passagesand said second andthird passages, and said fifth Vand sixth passages connected to saidsecond conduit means.

V4. An apparatus as defined in claim 3 in which said l second conduitmeans includes a fifth conduit connected to said fifth passage and saidsuction of said pump, a sixth condult connected to said sixth passageand the interior of said reservoir, and said member in said valve whenin said second position establishing communication between said fourthand fifth passages yand said first and sixth passages.

5. An apparatus as defined in claim 3 in which movement of said valvemember in said valve body is in response to hydraulic fluid pressureexerted thereon, and a pilot valve is provided that controls hydraulicfluid under pressure that is caused to be exerted on said valve ,memberin response to reciprocation of said loaded rod.

6. An apparatus as defined in claim 3 in which said means responsive tothe second pressure of said gas in said reservoir and the first pressureof said uid in said first portion of said cylinders is a hollowcylindrical body in which a piston is slidably mounted which has twopiston rods extending outwardly from opposite sides thereof-throughksaid body, the end interior portions of said body in communication withsaid gas in said reservoir and said fluid in said first portion of saidcylinders, with a normally closed bleed-off Valve being provided that isin communication with said gas in said reservoir, and `said piston whensaid pressure of said gas in saidreservoir attains more than apredetermined differential relative to said fluid at said first pressuremoving in a direction to cause one of said piston rods to actuate saidbleed-off valve to assume an open position until sufficient of said gasin said reservoir has escaped through said bleed-off valve to permitsaid piston in said body to move out of said position in which saidbleed-off valve is actuated.

7. An apparatus as defined in claim 6 in which a valve is provided thatcontrols the air supply tov said clutch, and said piston in said bodywhen said gas pressure in said reservoir falls below said differentialrelative to said pressure onV said fluid in said first portion ofcylinders, moving in a direction to cause one of said rods project- `ingfrom said piston to actuate said air control valve until said airpressure in said reservoir has built up to said predetermineddifferential relative to said pressure of said uid in said first portionof cylinders.

8. In a hydraulically operated unit to reciprocate a substantiallyvertically disposed loaded rod of the type of unit which includes afirst cylinder with a first piston movably disposed therein that raisessaid rod when a hydraulic fluid under pressure is discharged into saidfirst cylinder, a second cylinder and second piston movably disposedtherein, which second piston partially supports said load on said rod oneach upstroke and downstroke thereof when'hydraulic uid under pressureis maintained in said second cylinder, said first and second pistonsbeing rigidly connected to said rod, the improvement in which thedownward movement of said rod is maintained at a desired uniform rateirrespective of variation in the load on said rod comprising: a positivedisplacement pump capable of discharging hydraulic iiuid under pressurewhen actuated; a prime mover that actuates said pump at a constantpumping rate; a reservoir of suflcient volume to hold a quantity of saidhydraulic iiuid greater than that required to be discharged into saidfirst cylinder to raise said piston and rod on said upstroke apredetermined distance and to cause said second piston at all times topartially support said load on said rod; first Valve means that includesa body having first, second, third, fourth, fifth and sixth fluidpassages formed therein, and a valve member movably mounted in saidbody, said valve member capable of occupying a first position in whichsaid first and fourth passages are in communication as are said secondand third passages, and a second position in which said fourth and fthpassages are in communication as are said first and sixth passagesyafirst conduit connected to the discharge of said pump and said rstpassage; a second conduit connected to the interior of said reservoirand said second passage; a third conduit connected to said third passageand the suction of said pump; a fourth conduit connected to said fourthpassage and the interior of said first cylinder; a fifth conduitconnected to said fifth passage and said suction of said pump; a sixthconduit connected to said sixth passage and the interior of saidreservoir;

a seventh conduit connected to the interior of said reservoir and saidsecond piston; means that at all times maintain at least a predeterminedminimum pressure on said fluid in said reservoir to exert an upwardforce on said second piston at all times to partially support said loadon said rod; means responsive to the movement of said rod that movessaid valve member to said first position as said first piston approachesthe completion of its downstroke and to said second position upon saidrod being raised on the upstroke thereof to a predetermined elevation,said Valve member in said first position permitting said pump to drawsaid fluid from said reservoir through saidsecond and third conduitsfrom said reservoir under a head of at least said minimum pressure anddischarge said hydraulic iiuid through said first and fourth conduits tosaid first cylinder to raise said rod to said predetermined elevation,with said valve member in said second position permitting the portion ofsaid load on said rod not supported by said second piston to move saidrod downwardly with concurrent discharge of said fluid from said firstcylinder through said fourth and fifth conduits to the suction of saidpump to be discharged therefrom through said first and sixth conduits tothe interior of said reservoir, and said pump when discharging saidfluid through said first and sixth conduits acting as la regulator tocontrol the rate at which said rod moves on said downv stroke thereof.

9. In a hydraulically operated unit as defined in claim 8 in which saidmeans to maintain said substantially constant head on said fluid in saidreservoir is a quantity of a gas disposed therein that is at all timesmaintained above the predetermined pressure required for said secondpiston to support said desired portion of said load on said rod on boththe upstroke and downstroke thereof.

10. in a hydraulic pumping unit as defined in claim 9 in which a desireddifferential is automatically maintained between the pressure on saidfluid in said firstV cylinder and said pressure on said gas in saidreservoir by providing a source of said gas at a pressure substantiallygreater than said minimum pressure, a normally closed gas bleed olfvalve on said reservoir, means which when actuated result in the flow ofsaid gas from said source to said reservoir, and a pressure-comparingmechanism including a movable member, said mechanism at all times incommunication with said gas in said reservoir and said fluid in saidfirst cylinder, said member responsive to a predetermined differentialin pressure between the pressure on said uid in said rst cylinder andthe pressure on said gas in said reservoir, said member being moved to afirst position when the pressure on said uid in said first cylinderexceeds said predetermined differential relative to said gas in saidreservoir, said member in said first position actuating said means topermit iiow of said gas to said reservoir, said member being moved to asecond position when the pressure on said gas in said reservoir exceedssaid predetermined differential relative to said pressure of said Huidin said rst cylinder, said member when in said second positionmaintaining said bleed-off valve in an open position to permit dischargeof said gas to the ambient atmosphere until the difference in pressuresbetween said gas in said reservoir and said Huid in said first cylinderis at said predetermined differential.

References Cited in the le of this patent

